Biochemistry of Amino Acids

Biochemistry of Amino Acids - Chemistry of Amino Acids...

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Chemistry of Amino Acids Amino Acid Classifications Acid-Base Properties Functional Significance of R-Groups Optical Properties The Peptide Bond Custom Search Return to Medical Biochemistry Page Chemical Nature of the Amino Acids All peptides and polypeptides are polymers of α-amino acids. There are 20 α-amino acids that are relevant to the make-up of mammalian proteins (see below). Several other amino acids are found in the body free or in combined states (i.e. not associated with peptides or proteins). These non-protein associated amino acids perform specialized functions. Several of the amino acids found in proteins also serve functions distinct from the formation of peptides and proteins, e.g., tyrosine in the formation of thyroid hormones or glutamate acting as a neurotransmitter. The α-amino acids in peptides and proteins (excluding proline) consist of a carboxylic acid (– COOH ) and an amino (– NH 2 ) functional group attached to the same tetrahedral carbon atom. This carbon is the α-carbon. Distinct R-groups, that distinguish one amino acid from another, also are attached to the alpha-carbon (except in the case of glycine where the R-group is hydrogen). The fourth substitution on the tetrahedral α-carbon of amino acids is hydrogen. Object 1 Object 2 Search
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Table of α-Amino Acids Found in Proteins Amino Acid Symbol Structure * pK 1 (COOH) pK 2 (NH 2 ) pK R Group Amino Acids with Aliphatic R-Groups Glycine Gly – G 2.4 9.8 Alanine Ala – A 2.4 9.9 Valine Val – V 2.2 9.7 Leucine Leu – L 2.3 9.7 Isoleucine Ile – I 2.3 9.8 Non-Aromatic Amino Acids with Hydroxyl R-Groups Serine Ser – S 2.2 9.2 ≈13 Threonine Thr – T 2.1 9.1 ≈13 Amino Acids with Sulfur-Containing R-Groups Cysteine Cys – C 1.9 10.8 8.3 Methionine Met – M 2.1 9.3 Acidic Amino Acids and their Amides
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Asp – D 2.0 9.9 3.9 Asparagine Asn – N 2.1 8.8 Glutamic Acid Glu – E 2.1 9.5 4.1 Glutamine Gln – Q 2.2 9.1 Basic Amino Acids Arginine Arg – R 1.8 9.0 12.5 Lysine Lys – K 2.2 9.2 10.8 Histidine His – H 1.8 9.2 6.0 Amino Acids with Aromatic Rings Phenylalanine Phe – F 2.2 9.2 Tyrosine Tyr – Y 2.2 9.1 10.1 Tryptophan Trp – W 2.4 9.4 Imino Acids Proline Pro – P 2.0 10.6
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Biochemistry of Amino Acids - Chemistry of Amino Acids...

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